Improved battery safety via in-situ dip-coated composite gel polymer electrolytes

A new type of PVC-CPVC-MBS-B44 composite gel polymer electrolyte (GPE), based on LiTFSI and incorporated with nano-silica, is designed. The adhesion of the electrolyte membranes is improved by introducing B44, with its excellent adhesion ability, into the GPEs. The GPE membrane is coated on the anodes by an in-situ dip-coating process for battery assembly, reducing the interfacial resistance of the battery. The PVC-CPVC-MBS-B44 composite GPE exhibits superior electrochemical performance. The electrochemical window is over 4.9 V (vs. Li/Li⁺), the ion conductivity is 0.96 × 10^{- 3} S cm⁻¹ at an ambient temperature, and the lithium ion transference number is 0.61. The LiCoO₂/PVC-CPVC-MBS-B44 composite GPE/graphite cells exhibit maximum discharge capacities of approximately 137.98, 136.5, and 129.4 mAh g⁻¹ at 0.2C, 0.5C, and 1C discharge rates, respectively. The cells with GPE can maintain a high discharge capacity of 116 mAh g⁻¹ and a capacity retention exceeding 82.9% after 200 cycles at 0.5C. Heavy impact, nail penetration, crush test, short-circuit test, drop test and heating test are carried out on 1-Ah GPE pouch cells, and the battery does not ignite nor smoke. A battery prepared using the proposed approach can deliver outstanding safety, high rate capabilities, and superior cycle stability, making it a potential candidate for various applications.